Heretofore, a hydrochlorofluorocarbon (hereinafter referred to as “HCFC”) such as dichloropentafluoropropane (hereinafter referred to as “R-225”) was widely used as a fluorocarbon solvent for precision cleaning in order to remove oils, flux, dust, waxes and the like adhering to articles, e.g., during processing and machinery steps in the precision instrument industry, the optical instrument industry, the electrical and electronic industry, the plastic processing industry, and so on.
However, use of HCFC will be totally abolished in advanced countries until 2020 because of its ozone depletion potential. Hydrofluorocarbon (hereinafter referred to as “HFC”), hydrofluoroether (hereinafter referred to as “HFE”) and the like are known as fluorocarbon solvents which are alternatives for HCFC, which contain no chlorine in their molecule and which have the ozone depletion potential of zero.
For example, there is a known method for cleaning an article composed of a printed-circuit board, metal and so on, with the use of HFE having a boiling point of about from 20 to 120° C. (cf. Patent Document 1). However, this method often fails to adequately remove a contaminant because the solvency of HFE for the contaminant is not sufficient. There is another known method for cleaning an article with the use of an aliphatic hydrocarbon or the like.
However, there was a problem that these hydrocarbon solvents were unlikely to dry and a lot of energy was thus required to dry the article after cleaning, though these hydrocarbon solvents have the ozone depletion potential of zero and high removal efficiency of the contaminant.
A method for rinsing with HFE after cleaning with a hydrocarbon solvent (cf. Patent Document 2) was proposed as a method to solve the problem. However, this document fails to disclose a specific example of HFE.
However, even in the above method, HFE has a low solubility for the hydrocarbon solvent used for cleaning, depending on its kind, and the hydrocarbon solvent cannot be sufficiently removed by rinsing the article to be cleaned, with HFE, so that the hydrocarbon solvent remains on a surface of the article to be cleaned; this caused a problem of defective rinsing such as occurrence of stain.
Patent Document 1: JP-A-H05-271692 (claims)
Patent Document 2: JP-A-H10-202209 (claims)